FEATURES Video IF amplifier with synchronous demodulator Automatic gain control (AGC) detector suitable for negative modulation AGC tuner Automatic frequency control (AFC) circuit with sample-and-hold Video preamplifier Sound IF amplifier and demodulator DC volume control or separate supply for starting the horizontal oscillator Audio preamplifier Horizontal synchronization circuit with two control loops Vertical synchronization (divider system) and sawtooth generation with automatic amplitude adjustment for 50 and 60 Hz Transmitter identification (mute) GENERAL DESCRIPTION The TDA8303/TDA8303A combines all small signal functions (except the tuner) which are required for a monochrome television receiver. For a complete black and white receiver only the output stages for video, sound, horizontal and vertical deflection and a tuner have to be added. The TDA8303 is for applications with npn tuners and the TDA8303A for pnp tuners. FUNCTIONAL DESCRIPTION Video IF amplifier, demodulator and video amplifier Each of the three AC-coupled IF stages permits the omission of DC feedback and possesses a control range in excess of 20 dB. An additional advantage is the symmetry of the amplifier which results in a less critical application. ORDERING INFORMATION EXTENDED TYPE NUMBER TDA8303 TDA8303A Note SOT117-1; 1996 December 3. July 1992 2 PACKAGE PINS 28 PIN POSITION DIL MATERIAL plastic

The IF amplifier is followed by a passive synchronous demodulator providing a regenerated carrier signal. This is limited by a logarithmic limiter circuit prior to its application to the demodulator. The limiter has a very low differential phase shift which results in good differential gain and phase figures. The video amplifier also contains a white spot inverter and a noise clamp which limits interference pulses to a point below the peak sync level. This circuit is more effective than a noise inverter and results in an improved picture stability, with respect to interference. AFC-circuit The reference signal for the AFC circuit is obtained from the demodulator tuned circuit. In this way only one tuned circuit needs to be applied and only one adjustment has to be carried out. The disadvantage with this method is that the frequency spectrum of the signal fed to the detector is determined by the SAW filter characteristic. This spectrum is asymmetrical with respect to the picture carrier so that the AFC output voltage is dependent on the video signal. To overcome this video frequency dependency of the AFC output, the demodulator output is followed by a sample-and-hold circuit which samples during the sync level of the signal. This means that only the carrier signal is available to the AFC and it will not be affected by the video information. At very weak input signals the drive signal of the AFC circuit will contain substantial noise. This noise has an asymmetrical frequency spectrum causing an offset in the AFC output voltage. This effect can be minimized by applying a notch in the demodulator tuned circuit. The sample-and-hold circuit is followed by an amplifier with high output impedance, therefore the steepness of the of the AFC control voltage is dependent on the load impedance.

Notes to the quick reference data 1. Pin 11 has a double function. When during switch-on a current mA is supplied to this pin, it is used to start the horizontal oscillator. The main supply can then be obtained from the horizontal deflection stage. When no current is supplied to this pin it can be used as a volume control. 2. On set AGC. 3. The output signal is measured = 7.5 kHz and maximum volume control. 4. The minimum value is obtained by connecting 1.8 k resistor and 470 nF capacitor in series between the video output and pin 25. The slicing level can be varied by changing the value of this resistor (higher resistance value results in a larger value of the minimum sync pulse amplitude). The slicing level is independent of the video information.